Elastic-plastic J-R curves were obtained for compact specimens of A533B-02 plate tested at average load point velocities of 2.5 × 10−4 m/min and 0.25 m/s directly from the load displacement record using a key curve analysis technique. The slow velocity results compare well with J-R curves obtained on the identical specimens using an unloading compliance technique. The key curve method is shown to accurately predict the extent of crack extension. The J-R curves obtained from the high speed loading are shown to be elevated with respect to the slow test results in both the initial JIc and the tearing modulus T by from 50 to 100 percent.